1. Field of the Invention
The disclosed embodiments of the present invention relate to power control, and more particularly, to a power supply system capable of selectively switching a supply source of a control power required by a power control module.
2. Description of the Prior Art
In a conventional switching power supply, a main power conversion circuit (e.g. a power factor correction circuit and a power conversion circuit) is used for providing a power output, and an auxiliary power module is used for providing a control power required by a control module of the main power conversion circuit in order to help activate the main power conversion circuit, wherein the auxiliary power module further provides a power output in a standby mode (the main power conversion circuit is turned off). As the power output in the standby mode is only required to maintain basic operations, the auxiliary power module employs a low conversion efficiency structure to reduce manufacturing costs. For example, a flyback circuit structure is utilized to implement the auxiliary power module, wherein conversion efficiency of the flyback circuit structure is about 70%. However, low conversion efficiency represents high internal loss. This causes a large amount of power losses in the auxiliary power module, and degrades total conversion efficiency of the switching power supply.
Thus, there is a need for a novel power conversion structure to realize a power supply system having high conversion efficiency.